Glass carving. It was not possible until the 17th century. Craftsmen worked with Venetian glass. The Italians adopted the secrets of its production from the Byzantines. Oriental glass was brought from Constantinople to Rome in the 13th century. Glassblowers of Byzantium gave out secrets only after the capture of their state. The crusade took place in 1204.
Having adopted the secrets of glass-blowing art from the Byzantines, Italians made thin and fragile glass. The monk Fra Fabro wrote about him like this: “Nowhere can you find people who make vases of such a delicate material of such a transparent beauty of forms, which puts them above gold”. You can buy Bohemian crystal at https://aleks-crystal.com/tea-set/.
However, the Czechs were not satisfied with the fragility of Venetian glass. In Bohemia, they wanted to cut the material, seeing in its transparency a resemblance to diamond and rock crystal.
Italian glass crumbled when cut and polished. Then, the Czech masters changed the recipe of the material. Since then, Bohemian glass has overshadowed the Venetian glass with its fortress, brilliance and glory. Italian glass is composed of silica and alkalis. The latter determine the quality of the material. Legend has it that the first glass is soda melted in a fire. Its piece was among the wood.
In the morning, travelers, warming themselves by the fire, discovered glass. The fire appeared to have been on sandy soils. Their basis is silica, that is, silicon oxide. In mineralogy I call it quartz. Colored oxide with impurities. So, silica with manganese is amethyst stone. The pure formula of quartz is rock crystal. That is, glass is based on natural minerals. In fact, the material is recycled stone or, as they call it, artificial.
Bohemian glassmakers have added beech ash to the silica. She replaced soda in Italian products. Ash, called potash, is also carbonate. However, sodium is present in soda, and potassium in wood waste. The latter maximizes the colorlessness of the glass. Hence the active refraction of light and sparkle.
Lead oxide also improved the optical performance. In nature, the latter is found in the form of the cerussite mineral. 6% addition to the basic composition of glass makes it 2-3 times stronger than usual.
This gave the right to the material from Bohemia to be called crystal. The strength is due to the increased density. Due to lead oxide, it reaches 4.5 grams per cubic centimeter. For comparison, natural quartz has a density less than 2.8 grams. It turns out Bohemian glass is an order of magnitude harder than amethysts, rauchtopaz, citrines and the same rock crystal. Lead oxide is heavy. It is due to her that the vases made of Bohemian glass are so weighty. Elite samples are considered with 30-35% oxide content. In the official nomenclature, this is the premium class. Crystal with 25-30% addition of lead oxide is recognized as standard. 24% correspond to the item “Traditional Bohemian Glass”. The lower content of lead compounds is not typical for products from the Czech Republic.